Summary Symptoms of Autism Spectrum Disorder (ASD) extend beyond the traditional diagnostic triad of social cognition deficits, communication impairments, and limited interests / repetitive behaviors. Converging evidence supports the presence of motor abnormalities in the domain of postural control, including balance and gait. The understanding of these impairments is limited. The long-term goal of our team is to identify mechanisms underlying motor and postural impairments in ASD to further the understanding of the bases of ASD. The proposed project represents an initial step in a program of research designed to identify potential mechanisms underlying motor and postural impairments in ASD. More specifically, here we focus on links between postural/locomotor control and cognition (specifically the top-down regulation of access to the limited process of action control, or `attention for action') in ASD. Our main hypothesis is that postural control difficulties in ASD are due to problems in attention-related processes, which then elicit action control that transiently inhibits action, slowing appropriate postural adjustment. We will test this hypothesis by using dual-task paradigms that combine information-processing (IP) tasks and challenging posture/locomotor tasks. These tasks add an additional requirement for action and thus probe the capacity of the action control process. Thirty young adults diagnosed with ASD (21-45 years old) and 30 age-, gender- and IQ- matched controls will be tested. The dual-task paradigms will include IP tasks (simple and choice reaction time tasks) concurrently presented with standing and walking tasks requiring sensorimotor re-weighting. Simple reaction time tasks minimally challenge action control, while choice reaction time tasks probe decision-making between alternative actions, thus challenging action control more than simple reaction time tasks. Potential findings of the proposed project will enhance our understanding of the etiology of motor impairments and functional consequences of balance difficulties in ASD, both of which may contribute to the development of novel and more effective therapeutic approaches.